Dishwashers are widely used both domestically as well as in mass eating places, e.g. restaurants. In such systems, a detergent, which may be a dry detergent, e.g. supplied as a powder, or a liquid detergent is applied onto the dishes at predetermined parts of the washing cycle. In certain dishwashers a combination of detergents is used.
Detergents can have an acidic pH or an alkalinic pH. There are advantages in using detergents giving rise to a high pH when being in solution, as well as such giving rise to a low pH. U.S. Pat. No. 5,338,474 (Fitch et al.) discloses a powdered automatic dishwashing detergent composition which, once in solution imparts on the solution a pH of 8-13, preferably 9-12. The composition of Fitch et al. is specifically suitable for removal of carbonoid stains from plastic ware. A composition having an alkalinic pH is also disclosed in International (PCT) Patent Application, WO 96/17047. An acidic detergent is disclosed in PCT Application 96/15215. The detergent of this patent has a pH lower than 2, and is useful in the food industry.